1. Field of the Invention
Exemplary aspects of the present invention relate to a reuse method and an image forming apparatus, and more particularly, to a reuse method and an image forming apparatus for efficiently reusing a reusable device and a sensor in another image forming apparatus.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, and multifunction devices having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a recording material (e.g., a sheet) based on image data using electrophotography.
For example, when an electrostatic latent image is formed on a surface of a photoconductor, serving as an image carrier, a development device develops the electrostatic latent image with a developer (e.g., a two-component developer) into a visible toner image. The two-component developer includes toner and carrier. The development device stirs the toner and the carrier to charge them by friction. Then, when the charged toner adheres to an electrostatic latent image formed on an image carrier, a toner image is formed as a visible image.
In order to form a toner image on the image carrier, as the development device supplies toner to the image carrier, the amount of toner remaining in the development device decreases, so that a ratio between the amount of toner and the amount of carrier in the developer changes from an original state. However, for good imaging quality, it is important to maintain a constant ratio between the amount of toner and the amount of carrier, which ratio is also hereinafter referred to as toner density. Therefore, one related-art image forming apparatus includes a toner density sensor to monitor the toner density. When the toner density sensor detects that the toner density falls below a threshold density, fresh toner is supplied to the development device so as to maintain a predetermined toner density.
The toner density sensor can be a magnetic sensor, which detects changes in toner density by detecting changes in magnetic permeability of the developer. However, since magnetic sensors in general tend to be highly sensitive, and tend to be affected by errors in the manufacture of components of the sensor and the like. Consequently, each magnetic sensor outputs a slightly different reading from any other, that is, handles the relation between toner density and output voltage differently.
In order to prevent such variations in accuracy of the magnetic sensor, the image forming apparatus performs an initial adjustment of a control voltage of the magnetic sensor before use of the development device. The new development device initially stores developer having a predetermined toner density of 5%, for example. While the development device stirs the developer, the magnetic sensor detects toner density. The image forming apparatus adjusts the control voltage of the magnetic sensor such that the output voltage of the magnetic sensor becomes a voltage of 3 V, for example, when the predetermined toner density is 5%. Having thus calibrated the relation between the toner density and the output voltage, thereafter, fresh toner is added to the development device to increase the toner density to, for example, 7%, or a level that is appropriate for good image formation.
The new development device initially has a toner density of 5%, that is, lower than the 7% appropriate for image formation, because typically toner stored in the development device at the beginning of use is not electrically charged and thus easily scatters when the developer is stirred. As the amount of toner stored in the development device increases, the toner density also increases. Therefore, the initial toner density in the new development device is purposely set low in advance, thereby reducing scattering of toner in initial stirring of the developer. Then, the toner is charged by stirring, and toner density is increased by adding more toner.
This matter of toner density and its control becomes important when it comes to attempting to recycle components of the image forming apparatus. Such recycling first requires a brief discussion of the structure of a typical image forming apparatus, which now follows.
Typically, related-art image forming apparatuses using electrophotography include a photoconductor carrying a toner image, a charger charging a surface of the photoconductor, an exposure device exposing the charged surface of the photoconductor to form an electrostatic latent image, and a development device supplying toner to the electrostatic latent image formed on the surface of the photoconductor to form a toner image thereon.
Each of the above devices has a different service life from any other. Thus, for example, the photoconductor has a shorter service life than that of the development device. Therefore, when the photoconductor reaches the end of its life, the development device and the toner density sensor can still be used in another image forming apparatus.
However, as any given image forming apparatus has a process linear velocity different from that of any other image forming apparatus, the calibration of the toner density sensor for one development device, that is, the adjustment of the relation between the toner density sensor and the output voltage determined at the process linear velocity of the image forming apparatus which has used the development device and the toner density sensor, cannot usually be directly applied to another image forming apparatus without some adjustment. In other words, the toner density sensor needs to be calibrated again to set the correct, predetermined relation between the toner density and the output voltage for any given development device of any given image forming apparatus.
However, in order to adjust the control voltage of the toner density sensor, the toner density in the development device needs to be precisely known. Since the development device has already been used, the toner density in the development device differs from the initial toner density (5%), and it is difficult to know an exact toner density in the development device. Therefore, when the development device and the toner density sensor are reused, the toner density sensor cannot precisely detect the toner density.
Accordingly, there is a need for a technology capable of providing a method of reusing a development device and a toner density sensor as described above.